Electronic and computerized graphics systems are known. in the art. Typically, they offer a user the ability to produce a color image and from the image, to produce s picture which can either be printed via a color reproduction system, such as a plotter or a printer, displayed on a video screen or saved in memory.
It will be noted that in the context of the present specification, an "image" is a graphical creation created by a user within a computerized graphics system and a "picture" is a visual two-dimensional representation of the image.
The image can be produced through a number of methods as follows:
a) An image can be created graphically within the graphics system, as illustrated in FIG. 1A. The creation process emulates, in the mind of an operator 10, the process of creating an image 12 by moving an artistic tool 14, such as a pen, pencil, paintbrush, etc., along a surface 16. In reality, the operator 10 operates on a picture 18, or representation, of image 12 which is displayed on a display device 20. There is no picture of the surface 16; rather, the image 12 is produced on a plain, typically white background. PA1 b) A new image can be created from a previous image via graphical manipulations on the previous image. The previous image can be one which was created graphically or one which was received from a scanning system. PA1 c) Two images can be merged together and then manipulated graphically. This method often entails use of masks for masking those portions of one of the images which are not to be combined with the other image. Limits are also utilized, in conjunction with masks, to define areas of the resultant image where an icon cannot operate.
The creation operation is performed typically via manipulation of a cursor manipulation device 24, operating in conjunction with a computing device 26, which manipulation produces movement of an icon 22 on display device 20. Together, the devices 24 and 26 are operative to emulate a plurality of artistic tools 14 and as such form a tool emulating system 28, denoted with a dotted line. Each emulated tool has its own properties, such as the thickness of the line which it will draw, and its location and tool type are represented on device 20 via a representative icon 22. The emulated tool is a software entity and therefore is not shown in the Figure. Through manipulation of the emulated tool, image 12 is created or modified.
The emulated tool is operative to emulate the "look and feel" of standard artistic tools 14 such as paint brushes, pieces of chalk, and even human fingers (in an emulated tool known as "smudge"). The term "artistic tools" refers hereinafter to physical tools used to create a piece of art.
For example, GB Patents 2,140,257 and 2,089,625 describe a video image creation system which emulates the feel of an artistic tool 14 as well as many aspects of a color medium it carries.
The cursor manipulation device 24 can be a mouse, a stylus or a puck, which interactively acts in real time. Activation of the device 24 can occur for as long as the user presses on a button, or buttons, of the tool, or the device 24 can trigger on or off the action of icon 22. For some devices 24, such as the SP300 stylus of Wacom of Tokyo, Japan, the button is operative to give a graduated response wherein the depth the button is pressed affects certain parameters of the graphics tool. Typically, the device 24 is connected to a graphics work-station.
Masks are typically defined by the amount of interaction between the images to be merged which is allowed. A "hard" mask is a binary mask which simply omits that which is masked out and includes all the rest. A "soft" mask is a typically multiple bit mask which defines a multiplicity of levels of interaction. Thus, the extent to which a pixel of one image is omitted depends on the intensity value of the corresponding pixel in the soft mask.
Masks and apparatus for implementing them are described in detail in GB Patents 2,157,122 and 2,113,950.
A graphics system can produce images in either the vector or bitmap format. In vector format, objects in the image are mathematically defined as geometric shapes, such as squares, lines, triangles, circles etc. Each object can be given graphic characteristics such as color, and the order in which the objects are defined is saved. A bitmap image processor is utilized to produce the representation 18 of the image on the display 20, which is in bitmap format. As is known in the art, the resolution of the bitmap produced by the bitmap image processor is matched to the characteristics of the output device, whether it be a display device, such as a monitor, a printing device, or a transmission device for transmitting the picture to a receiving device, such as a television screen or a facsimile.
In bitmap format, the entire picture is saved as a collection of individual picture elements, or pixels, wherein each pixel has a given color There are no relationships among the pixels and the resolution of the bitmap is fixed.
Some graphics systems include various ones of the elements outlined hereinabove. All such systems enable a user to produce an image from an already existent image through graphic manipulation of the image using graphics tools such as masks and/or icons.
Examples of graphics application software useful in electronic and computerized graphics systems are the Adobe Photoshop, a bitmap-based software package, and the Adobe Illustrator, a vector-based software package, both manufactured by Adobe Systems Incorporated of Mountain View, Calif., U.S.A., and the Pixel Paint manufactured by Supermac Technology of Sunnyvale, Calif., U.S.A. All of the programs operate on the Apple Macintosh personal computer manufactured by Apple Computers Inc. of Cupertino, Calif., U.S.A.
Other types of computerized graphics systems include Computer Aided Visualization (CAV) systems. Operators of CAV systems create three-dimensional objects, defined in the vector format, and then imitate the look of the object in as realistic a manner as possible using rendering techniques. The technique producing the most realistic results is ray tracing.
In ray tracing, the paths of all the light rays impinging on a surface are traced in order to calculate the total light illuminating each point on that surface. The interaction of the ray and the surface of the object is calculated, in accordance with the laws of physics, as a function of the angle of the ray, the amount of light which is reflected and/or absorbed by the object and other parameters, such as the color of the object and the color of the light.
Ray tracing calculations are computer-intensive and are therefore, not interactive, nor do they enable real-time operation. The user must build the object or composition of objects to which he must impart characteristics with respect to light, such as color, amount of light it can absorb, etc.. He must also add a light source, with its characteristics, somewhere in the space around the object or objects, and then he must indicate to the system to produce a two-dimensional bitmap of the composition. The system may take a number of hours to produce the bitmap which is a fairly realistic two-dimensional representation of the composition.
Example ray tracing systems are the Stratavision manufactured by Stratavision Inc. of St. George, Utah, U.S.A. and Integrates manufactured by Intergraph Corporation of Huntsville, Ala., U.S.A. Both programs operate on the Apple Macintosh.
There also exist software packages which impart the physical and aesthetic characteristics of a given material to a three-dimensional object for later ray tracing.
There has been an effort, in the prior art, to produce images which closely match reality whether by matching the qualities of the emulated tools to those of artistic tools or by defining the properties of a geometrical composition.
However, the current state of the art does not consider how a physical substrate, such as smooth paper, cloth, or a fibrous material, affects the look of an image. Rather, all images are represented as having no physical substrate. Artists and the like understand that substrates affect the look of the image and therefore, choose their substrates carefully.
Similarly, the physical properties of the medium giving color to the image affect the appearance of the final picture or painting. Typical media giving color to an image are water-based and oil-based paints, charcoal, crayons, colored pencils, etc. Properties of each medium, such as mass, volume, color, fluidity, granularity, drying speed and hardness when dried, vary among different media.